<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>location地址栏对象</title>
  <style>
    p{
      text-align: center;
    }
    span{
      color: red;
    }
  </style>
</head>
<body>
    <p>
  注册成功！<span id="time">5</span>秒之后自动跳转到首页...
    </p>
</body>
    <script>
      let num=5;

      function show(){
        num--;

        if(num<=0){
          //跳转首页
          location.href="https://www.bilibili.com/";
        }

        let id = document.getElementById("time");
        id.innerHTML=num;
      }


      //循环定时器，每1秒执行show方法
      window.setInterval("show()",1000);
    </script>
</html>